The present invention relates to an apparatus for generating microwave and millimeter wave radiation by stimulating the coherent emission of cyclotron radiation from a beam of free electrons.
The relativistic electron cylotron master (commonly called a gyrotron) is a microwave device based on the cyclotron maser interaction between an electromagnetic wave and an electron beam in which the individual electrons move along helical trajectories in the pressure of an applied magnetic field. In the gyrotron oscillator the electron beam sustains a constant-amplitude normal-mode oscillation in an open-end cavity.
The primary motivation for achieving a high-efficiency gyrotron is connected with its application in controlled-fusion research. To reach the fusion ignition temperature, a great amount of energy (many megajoules) has to be injected for plasma heating. Furthermore, this should be done with the maximum efficiency in order to alleviate the energy break-even condition. A highly efficient gyrotron has been recognized as one of the most promising sources to meet these requirements.
Two commonly used definitions of efficiency need to be distinguished. The overall efficiency (.eta.) is defined as the average electron-energy loss divided by its total initial energy, and the transverse efficiency (.eta..perp.) is the same quantity divided by the initial transverse energy.
Many methods for efficiency enhancement have so far been considered. However, in the past, the maximum transverse efficiency was limited to about 40 percent.